Alternating-current wattmeter.



No. 760,426. PATENTED MAY 24, 1904. F. CONRAD.

ALTERNATING CURRENT WATTMETER.

APPLICATION FILED T33. 20. 1903.

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No. 760,426. PATENTED MAY 24, 1904. Fr CONRAD.

ALTBRNATING CURRENT WATTMBTER.

APPLICIATION FILED FEB. 20' 1903.

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No. 760,426. PATENTED MAY 24, 1904. F. CONRAD. ALTBRNATING CURRENTWATTMETER.

' APPLIUATION FILED FEB. 20. 1903. N0 MODEL. 7 3 SHEETS-SHBET 3.

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PATENT OFFICE.

FRANK CONRAD, OF EDGEWOOD PARK, PENNSYLVANIA, ASSIGNOR TO WESTINGHOUSEELECTRIC & MANUFACTURING COMPANY, A CORPO RATION OF PENNSYLVANIA.

ALTERNATlNG-GURRENT WATTNIETER.

SPECIFICATION forming part of Letters Patent No. 760,426, dated May 24,1904. Application filed February 20, 1903. Serial No. 144,855. (Nomodel.)

.To a, whom it may concern:

Be it known that I, FRANK CONRAD, a citizen of the United States,residing at Edgewood Park, in the county of Allegheny and State ofPennsylvania, have invented a new and useful Improvement inAlternating-Current Wattmeters, of which the following is aspecification.

My invention relates to instruments employed for measuring the energy ofalternating-current circuits, and particularly to such instruments asregister the amount of energy supplied to translating devices during thetime in which the instruments are inservice.

The object of my invention is to provide a simple, reliable, andreadily-adjustable means for both securing quadrature relation betweenthe shunt and series fields of the instrument and compensating forfriction.

In the accompanying drawings, Figure 1 is a front elevation of awattmeter provided with my improvement, the front portion of the easingbeing removed. Fig. 2 isasectional view of the instrument at rightangles to the view shown in Fig. 1. Fig. 3 isa diagram of the circuitsand principal operating members of a wattmeter constructed in accordancewith my invention, and Fig. i'is a diagram of a modified form of myfriction-compensating means.

The instrument shown in Figs. 1, 2, and 3 is, as regards its generalform and its principal operating members, in all essential respects likethe subject-matter of Patent N o. 608, 84.2, granted to the WestinghouseElectric & Manufacturing Company, as assignee of H. P. Davis and myself,on the 9th day of August, 1898.

The instrument shown, being designed for the measurement of the energyof single-phase circuits, comprises two shunt-connected coils 1 and 1,which are joined togetherin series to operate as a single coil, aseries-connected coil 2, a laminated core 3 for said coils, aninductance-coil 4 for retarding the current in the shunt-circuit, arotatable disk 5 constituting the secondary member or armature, a

spindle 6 therefor, a gear-trainsupporting frame 7, a dial-plate 8, (thegear-train for receiving and transmitting motion from the spindle 6being omitted,) and a supportingframe 9 for said parts. For the purposeof inclosing and protecting the operating parts of the instrument I alsoprovide a casingfront 10, the face of which is provided with asight-pane 11 to permit of examination of the registering devices, and asight-pane 12 to permit of observing the movements of the disk 5.

In the patent above referred to means was provided for insuring exactquadrature relation between the magnetic flux due to the currenttraversing the series coil and that due to the current traversing theshunt-coils for a condition of no inductive load upon the external orwork circuit, some such means being necessary in order to secureaccurate registration of the energy of circuits having inductive loads.The means set forth in said patent consisted of two coils in inductiverelation to the shunt-coils of theinstrumcnt and connected together inseries through aresistance. The said patent also disclosed as afriction-compensating means a single closed coil in inductive relationto one of the shunt-coils of the instrument, and thereforeunsymmetrically placed with reference to the armature. By means of mypresent invention 1 am able to utilize a single means for securingquadrature relation between the two magnetic fluxes of the instrumentand also such compensation as may be necessary to eliminate the effectof that small degree of friction which is necessarily present wherethere are rotating parts.

As shown in Fig. 3, the quadrature-adjusting coils l3 and 14, which aredisposed upon and in inductive relation to respective shuntcoils 1 and1, have corresponding terminals connected to the respective ends of aresistance-wire 15, upon which is mounted an adjustable contactpiece 16,this piece being here shown as a short tube, in one end of which ismounted a set-screw 17 for fastening it in any position upon the wire 15to which it may be moved. Any other suitable form of adjustable contactdevice may obviously be employed in lieu of that shown. The other endsof the coils 13 and 1d are connected together and are joined by means ofconductors 18, 19, and 20 to corresponding terminals of two ohmicresistances 21 and 22, the other terminals of these resistances beingconnected by means of conductors 23, 24:, and 25 to the adjustablecontact device 16, the conductor 25 being of such length and flexibilityas will permit of any desired degree of movement of the device 16 alongthe wire 15. This arrangement of apparatus is intended for circuits ofrelatively low frequency-such, for example, as seventy-two hundredalternations per minute. In the case of circuits of approximately doublethe above-mentioned frequency as, for example, those havingsixteenthousand alternations per minute-only one of the ohmic resistances needbe employed, and I therefore provide a soldered connection 26, which maybe unsoldered when the instrument is to be used in connection with thehigher rate of alternations. When this connection 26 is broken, thecircuits become, in effect, what is indicated in Fig. 1, the resistance22 being the only one in service.

lVith the arrangement of apparatus shown it will be seen that the coils13 and 14 are connected together in parallel, so that the current set upinductively in each coil must pass through either the resistance 21 orthe resistance 22, or both, these resistances being so adjusted as toafford the proper quadrature relation between the shunt and seriesfields of the instrument.

When the contact device 16 is located at the middle point of theresistance-wire 15, equal currents will flow through thetwo coils 13 and14:, and there will consequently be no unbalancing effect produced uponthe shunt-field. If, however, the contact device is moved toward one endof thewire, the resistance of the circuit of the coil toward which it ismoved will be reduced and the resistance of the circuit of the othercoil will be increased. follows, therefore, that the relation of thecurrents flowing through the two coils will be changed and an unbalancedeffect will be produced which will tend to drive the disk 5 in the onedirection or the other, according to the direction of movement of thecontact device. The contact device may therefore be set at such aposition that the torque pro duced upon the disk by the unbalancing willexactly counterbalance the retarding effect due to friction withoutappreciably changing the total resistance of the compensating circuit,and therefore without appreciably affecting the quadrature relation ofthe shunt and series fields of the instrument.

WVhile the specific devices shown and described have been designed forpractical service and have been found satisfactory, it is conceivablethat variations may be devised which will operate in substantially thesame way to produce the same result, and I therefore desire it to beunderstood that all such variations are within the spirit and scope ofmy invention.

I claim as my invention- 1. An alternating-current wattmeter providedwith two quadrature-adjusting coils that are substantially alike andsymmetrically disposed and are connected together in parallel circuit.

2. An alternating-current wattmeter provided with twoquadrature-adjusting coils connected together in parallel circuit andmeans for transferring resistance from the circuit of either of saidcoils to that of the other.

3. An alternating-current wattmeter provided with twoquadrature-adjusting coils connected together in parallel circuit, afixed resistance common to the circuits of said coils, a secondresistance andmeans for transferring any desired portion of the latterfrom the circuit of either coil to that of the other.

4. An alternating-current wattmeter provided with two quadrature-ad justing coils having two of their terminals connected together,

a resistance, to the ends of which the other terminals of the coils areconnected, a contact device movable along said resistance and anon-adjustable resistance having its respective terminals connected tothe movable contaclls device and to the connected ends of the 001 s.

5. An alternating-current wattmeter provided with twoquadrature-adjusting coils having two corresponding ends connectedtogether, a resistance-wire to the respective ends of which the otherends of the coils are connected, a contact device mounted upon said wireand movable longitudinally thereon and a non-adjustable resistancehaving its terminals connected respectively to the contact device and tothe joined ends of the coils.

6. An alternating-current wattmeter provided with twoquadrature-adjusting coils which have two corresponding ends connectedtogether, a resistance member to the respective terminals of which theother ends of the coils are connected, an adjustable contact devicemaking engagement with said resistance member and two non-adjustableresistances one or both of which may be connected between the contactdevice and the joined ends of the coils.

7. An alternating-current wattmeter having shunt and series field-coils,two like quadrature-adjusting coils symmetrically disposed in inductiverelation to the shunt field-coils and connected together in parallelcircuit and a resistance member any portion of which may be transferredfrom the circuit of either In testimony whereof I have hereunto subcoilto that of the other. scribed my name this 13th day of February,

8. An alternating-current wattmeter hav- 1903. ing shunt and seriesfield-coils, two like quad- FRANK CONRAD. 5 rature-adjusting coilssymmetrically disposed Witnesses:

in inductive relation to the shunt field-coils A. B. REYNDERS,

and connected together in parallel circuit. JAMES B. YOUNG.

